Field
The present disclosure relates generally to systems for creating a durable water-resistant and fire-resistant foam-based seal in the joint between adjacent panels. More particularly, the present disclosure is directed to providing an expansion joint seal system which includes a plurality of fire retardant, such as intumescent, members to protect the adjacent substrates and joint.
Description of the Related Art
Construction panels come in many different sizes and shapes and may be used for various purposes, including roadways, sideways, tunnels and other pre-cast structures. Where the construction panels are concrete, it is necessary to form a lateral gap or joint between adjacent panels to allow for independent movement, such in response to ambient temperature variations within standard operating ranges. These gaps are also used to permit moisture to be collected and expelled. Cavity walls are common in masonry construction, typically to allow for water or moisture to condense or accumulate in the cavity or space between the two exterior walls. Collecting and diverting moisture from the cavity wall construction can be accomplished by numerous well-known systems. The cavity wall is often ventilated, such as by brick vents, to allow air flow into the cavity wall and to allow the escape of moisture heat or humidity. In addition to thermal movement or seismic joints in masonry walls, control joints are often added to allow for the known dimensional changes in masonry over time. Curtain wall or rain screen design is another common form of exterior cladding similar to a masonry cavity wall. Curtain walls can be designed to be primarily watertight but can also allow for the collection and diversion of water to the exterior of the structure. A cavity wall or curtain wall design cannot function as intended if the water or moisture is allowed to accumulate or condense in the cavity wall or behind a curtain wall or rain screen design cannot be diverted or redirected back to the outside of the wall. If moisture is not effectively removed it can cause damage ranging from aesthetic in the form of white efflorescence buildup on surface to mold and major structural damage from freeze/thaw cycling.
Thus, expansion and movement joints are a necessary part of all areas of construction. The size and location of the movement depends on variables such as the amount of anticipated thermal expansion, load deflection and any expected seismic activity. Joint movement in a structure can be cyclical in design as in an expansion joint or in as a control joint to allow for the shrinkage of building components or structural settling. These movement joints serve an important function by allowing a properly designed structure to move and the joint to cycle over time and to allow for the expected dimensional changes without damaging the structure. Expansion, control and movement joints are found throughout a structure from the roof to the basement, and in transitions between horizontal and vertical planes. It is an important function of these expansion joints to not only move as intended but to remain in place through their useful lifespan. This is often accomplished by extending the length and/or width of the expansion joint system over or past the edge of the gap or joint opening to attach to the joint substrate or another building component. Examples of building components that would ideal to integrally join an expansion joint with and seal would be, although not limited to, waterproofing membranes, air barrier systems, roofing systems and transitions requiring the watertight diversion of rain water. Although these joints represent only a small percentage of the building surface area and initial cost, they often account for a large percentage of waterproofing, heat loss, moisture/mold problems and other serious interior and exterior damage during the life of the building.
Conventional joint sealants like gunnable sealants and most foam seals are designed to hold the water out of the structure or expansion joint. However, water can penetrate the joint substrate in many ways such as cracks, poor sealant installation, roofing details and a porous substrate or wall component. When water or moisture enters the wall the normal sealing function of joint sealant may undesirably retain the moisture in the wall. Foam joint seals known in the art typically rely on the application of an elastomer sealant on the primary or exposed face of foam to provide the water resistant function. Such joint seals are not waterproof, but retard the penetration of water into the joint by providing a seal between adjacent substrates for a time and under a maximum pressure. Particularly, such joint seals are not waterproof—they do not preclude water penetration under all circumstances. While this is helpful initially to keep water out of the joint and structure it does not allow for this penetrating water or moisture to escape.
Further complicating operation, some wall designs, such as cavity walls, allow for moisture to enter a first wall layer where it collects and is then directed to the outside of the building by flashing and weep holes. In these systems, water can sometimes be undesirably trapped in the cavity wall, such as at a mortar bridge in the wall, or other impediment caused by poor flashing selection, design or installation. When a cavity wall drainage system fails, water is retained within the structure, leading to moisture accumulating within in the wall, and to an efflorescence buildup on the exterior of the wall. This can also result in freeze-thaw damage, among other known problems.
To be effective in this environment, fully functional, foam-based joint seals require a minimum compression ratio and impregnation density. It is known that higher densities and ratios can provide addition sealing benefits. Cost, however, also tends to increase with overall density. There is ultimately a trade-off between compression ratio/density range and reasonable movement capabilities at about 750 kg/m3. As can be appreciated, this compressed density is a product of the uncompressed density of the material and the desired compression ratio to obtain other benefits, such as water resistance. For example, a foam having an uncompressed density of 150 kg/m3 uncompressed and compressed at a 5:1 ratio results in a compressed density of 750 kg/m3. Alternative uncompressed densities and compression ratios may reach that compressed density of 750 kg/m3 while producing different mechanical properties. It has been long known in the art that a functional foam expansion joint sealant can be constructed using an uncompressed impregnated foam density range of about 80 kg/m3 at a 5:1 compression ratio, resulting in a compressed density of 400 kg/m3. This functional foam expansion joint sealant is capable of maintaining position within a joint and its profile while accommodating thermal and seismic cycling, while providing effective scaling, resiliency and recovery. Such joint seals are not fireproof; but retard the penetration of fire into the joint by providing a seal which protects the adjacent substrates or the base of the joint for a time and under a maximum temperature. Particularly, such joint seals are not fireproof—they do not preclude the burning and decomposition of the foam when exposed to flame.
Another alternative known in the art for increasing performance is to provide a water resistant impregnated foam at a density in the range of 120-160 kg/m3, ideally at 150 kg/m3 for some products, with a mean joint size compression ratio of about 3:1 with a compressed density in a range of about 400-450 kg/m3, although densities in a broader range, such as 45-710 kg/m3 uncompressed and installed densities, after compression and installation in the joint, of 45 kg/m3 and 1500 kg/m3 may also be used. These criteria ensure excellent movement and cycling while providing for fire resistance according to DIN 4102-2 F120, meeting the Conditions of Allowance under UL 2079 for a two-hour endurance, for conventional depth, without loading, with one or more movement classifications, for a joint not greater than six inches and having a movement rating as great as 100%, without a hose stream test, and an ASTM E-84 test result with a Flame Spread of 0 and a Smoke Index of 5. This density range is well known in the art, whether it is achieved by lower impregnation density and higher foam compression or higher impregnation density and a lower compression ratio, as the average functional density required for an impregnated open cell foam to provide sealing and other functional properties while allowing for adequate joint movement up to +/−50% or greater. Foams having a higher uncompressed density may be used in conjunction with a lower compression ratio, but resiliency may be sacrificed. As the compressed density increases, the foam tends to retard water more effectively and provides an improved seal against the adjacent substrates. Additives that increase the hydrophobic properties or inexpensive fillers such as calcium carbonate, silica or alumina hydroxide (ATH) provided in the foam can likewise be provided in a greater density and become more effective. Combustion modified foams such as a combustion modified flexible polyurethane foam, combustion modified ether (CME) foam, combustion modified high resilience (CMHR) foam or combustion modified Viscoelastic foam (CMVE) can be utilized in the preferred embodiments to add significant fire resistance to the impregnated foam seal or expansion joint without adding additional fire retardant additives. Foam that is inherently fire resistant or is modified when it manufactured to be combustion or fire-resistant reduces the cost of adding and binding a fire retardant into the foam. This method has been found to be advantageous in allowing fire resistance in foam seals configured in very high compression ratios such 5:1 and higher.
By selecting the appropriate additional component, the type of foam, the uncompressed foam density and the compression ratio, the majority of the cell network will be sufficiently closed to impede the flow of water into or through the compressed foam seal thereby acting like a closed cell foam. Beneficially, an impregnated or infused open cell foam can be supplied to the end user in a pre-compressed state in rolls/reels or sticks that allows for an extended release time sufficient to install it into the joint gap. To further the sealing operation, additional components may be included. For example, additives may be fully or partially impregnated, infused or otherwise introduced into the foam such that at least some portion of the foam cells are effectively closed, or a hydrophobic or water resistant coating is applied. However, the availability of additional components may be restricted by the type of foam selected. Closed cell foams which are inherently impermeable for example, are often restricted to a lower joint movement range such as +/−25% rather than the +/−50% of open celled foams. Additionally, the use of closed cell foams restricts the method by which any additive or fillers can be added after manufacture. Functional features such as fire resistance to the Cellulosic time-temperature curve for two hours or greater can be however be achieved in a closed cell foam seal without impacting the movement properties. Intumescent graphite powder added to a polyethylene (PE), ethylene vinyl (EVA) acetate or other closed cell foam during processing in a ratio of about 10% by weight has been found to be a highly effective in providing flexible and durable water and fire resistant foam seal. While intumescent graphite is preferred, other fire retardants added during the manufacture of the closed cell foam are anticipated and the ratio of known fire retardants, added to the formulation prior to creating the closed cell foam, is dependent on the required fire resistance and type of fire retardant. Open celled foams, however, present difficulties in providing water-resistance and typically require impregnation, infusion or other methods for introducing functional additives into the foam. The thickness of a foam core or sheet, its resiliency, and its porosity directly affect the extent of diffusion of the additive throughout the foam. The thicker the foam core or sheet, the lower its resiliency, and the lower its porosity, the greater the difficulty in introducing the additive. Moreover, even with each of these at optimum, the additive will likely not be equally distributed throughout the foam, but will be at increased density at the inner or outer portions depending on the impregnation technique.
A known solution in the art is the use of foam segments bonded together to provide a lamination. However, lamination increases cost due to the additional time and labor required as a forming fixture is often required for construction of the lamination. The required time and labor is further increased if additional function coatings are required to create a composite material with the desired properties.
It is also known that the thin built-up laminations must be adhesively bonded to avoid separation, and therefore failure, under thermal shock, rapid cycling or longitudinal shear. Because of the cost to effectively bond the laminations, a cost/performance assessment sometimes produces laminations loosely held together by the foam compression rather than by an adhesive. While this is known in the art to be somewhat effective in low performance applications and OEM assembly uses, it also known that it cannot meet the demands of high movement seismic, shear, deflection joints or where fail-safe performance is required. In light of these issues, the preferred embodiment for a high movement impregnated foam expansion joint has been found to instead be a monolithic foam design comprised of a single impregnated foam core. However, lamination systems are often still considered desirable when the lamination adds a functional feature such as integrating a water resistant membrane, a fire resistant layer or other beneficial function.
Construction of lamination systems are typically considered undesirable or inferior for a high movement or rapid cycling fire resistant expansion joint sealant. The higher compression ratios and greater volumes of fire retardant additives are likely to cause the foam to fatigue more rapidly and to lose much of its internal recovery force. This proves problematic over time due to the anticipated exposure to movement and cycling as the impregnated foam will tend to lose its recovery force and rely more on the push-pull connection to the joint substrate. When foam laminations are vertically-oriented, the laminations can de-bond or de-laminate and separate from one another, leading to only the outer most lamination remaining attached to the joint substrate, resulting in the laminated foam joint sealant ceasing to provide either water, air or fire resistance.
A known alternative or functional supplement to the use of various impregnation densities and compression ratios is the application of functional surface coatings such as water-resistant elastomers or fire-resistant intumescents, so that the impregnated foam merely serves as a “resilient backer”. Almost any physical property available in a sealant or coating can be added to an already impregnated foam sealant layering the functional sealant or coating material, Examples would include but not limited to, fire ratings, waterproofing, color, UV resistance, mold and mildew resistance, soundproofing, impact resistance, load carrying capacity, faster or slower expansion rates, insect resistance, conductivity, chemical resistance, pick-resistance and others known to those skilled in the art. For example, a sealant or coating having a rating or listing for Underwriters Laboratories 2079 may be applied to an impregnated compressed foam to create a fire resistant foam sealant.
One approach to addressing the shortcomings has been the creation of composite materials, where the foam core—whether solid or composed of laminations of the same or differing compositions—is coated or surface impregnated with a functional layer, so that the foam is merely a resilient backer for the sealant, intumescent or coating, such that the composition and density become less important. These coatings, and the associated properties, may be adhered to the surface of each layer of a core or layered thereon to provide multiple functional properties. As can be appreciated, the composite material may have different coatings applied the different sides to provide desired property or properties consistent with its position. Functional coatings such as a water-resistant, sealant can protect the foam core from absorbing moisture even if the foam or foam impregnation is hydrophilic. Similarly, a functional coating such as a fire-rated sealant added to the foam core or lamination with protect a foam or foam impregnation that is flammable. A biocide may even be included. This could be layered, or on opposing surfaces, or—in the case of a laminate body—on perpendicular surfaces.
Additionally, it has become desirable, and in some situations required, for the joint sealant system to provide not only water resistance, but also fire resistance. A high degree of fire resistance in foams and impregnated foam sealants is well known in the art and has been a building code requirement for foam expansion joints in Europe for more than a decade. Fire ratings such as UL 2079, DIN 4102-2, BS 476, EN1399, AS1503.4 have been used to assess performance of expansion joint seals, as have other fire resistance tests and building codes and as the basis for further fire resistance assessments, the DIN 4102 standard, for example, is incorporated into the DIN 18542 standard for “Sealing of outside wall joints with impregnated sealing tapes made of cellular plastics—Impregnated sealing tapes”. While each testing regime utilizes its own requirements for specimen preparation and tests (water test, hose stream tests, cycling tests), the 2008 version of UL 2079, the ISO 834, BS 476; Part 20, DIN 4102, and AS 1530.4-2005 use the Cellulosic time/temperature curve, based on the burning rate of materials found in general building materials and contents, which am be described by the equation T=20+345*LOG(8*t+1), where t is time in minutes and T is temperature in C. While differing somewhat, each of these testing regimes addresses cycling and water resistance, as these are inherent in a fire resistant expansion joint. The fire resistance of a foam sealant or expansion has been sometimes partially or fully met by infusing, impregnating or otherwise putting into the foam a liquid-based fire retardant, such as aluminum tri-hydrate or other fire retardants commonly used to add fire resistance to foam. Unfortunately, this increases weight, alters the foam's compressibility, and may not provide the desired result without additional fire resistant coatings or additives if a binder, such as acrylic or polyurethane, is selected to treat the foam for fire and water resistance. Doing so while maintaining movement properties may affect the foam's compressibility at densities greater than 750 kg/m3. Ultimately, these specialty impregnates and infused compositions increase product cost.
It has further become desirable or functionally required to apply a fire resistant coating to the foam joint systems to increase fire and water resistance, but often at the sacrifice of movement. Historically, fire-resistant foam sealant products that use an additional fire resistant surface coating to obtain the life safety fire properties have been limited to only +/−25% movement capability, especially when required to meet longer time-temperature requirements such as UL2079's 2 hour or longer testing. This +/−25% movement range is too limited for most movement joints and would not meet most seismic movement and expansion joint requirements. One well-known method for utilizing these low movement fire resistant joint sealants is to increase the width or size of the joint opening, an undesirable and expensive alternative, to allow for a commonly required +/−50% joint movement rating.
Unfortunately, supplying a pre-coated foam seal from the factory requires long leads times due to the required curing time, which can often hold up completion of projects in the final stages. This shortcoming is exacerbated if the composite material requires an additional functional layer to provide the desired properties. Installing the foam seal and adding another sealant in the field eliminates the one-step advantage of pre-compressed foam seals. The required multi-step process is labor and skill intensive and becomes even more challenging when the joint becomes greater than one inch, which pose difficulties for installation and to provide an aesthetically pleasing finished joint seal
It would be an improvement to the art to provide an expansion joint seal which provided resistance to fire and water, retained compressibility over time, and did not require impregnating, infusing or compression forcing a large amount of solid fillers into the foam structure.